Manufacture of molybdenum and alloys thereof



United States Patent MANUFACTURE OF MOLYBDENUM AND ALLOYS THEREOF No Drawing. Application November 20, 1953 Serial No. 393,511

5 Claims. (Cl. 148--11.5)

This invention relates to molybdenum and its alloys, and more particularly to such of exceptionally uniform grain structure.

An object of our invention, generally considered, is to manufacture molybdenum, and alloys thereof with small proportions of other metals such as cobalt, nickel, iron and tungsten, in such a way that improved grain structure is obtained.

Another object of our invention is to obtain in refra'c'tory metals, by an improved working schedule, exceptionally uniform grain structure, high hardness, augmented ultimate strength, and a higher as worked elongation with minimum porosity. A" further object of our invention is to produce molybdenum, and alloys thereof with small proportions of cobalt, nickel, iron or tungsten, by a' swaging process involving first a treatment above recrystallization temperature, followed by a treatment below recrystallization temperature, the first treatment taking place during a single swaging pass, and the subsequent treatment occurring during a plurality of such passes.

' Other objects and advantages of the invention will become apparent as the description proceeds.

The properties of molybdenum, and alloys thereof with small proportions of metal selected from the group consisting of cobalt, nickel, iron and tungsten, are primarily dependent from the grain structure of the swaged, rolled or otherwise worked ingot. By the expression alloys of molybdenum with small proportions of metal selected from the group consisting of cobalt, nickel, iron and tungsten, we mean such in which the proportion of cobalt is not greater than .3%, in which the proportion of either of the alloying nickel or iron is not greater than /z%, an din which the proportion of the alloying tungsten is not greater than 25%, all proportions being by weight. -Although cobalt is preferred as the alloying metal, nickel and iron have similar effects. Tungsten has a similar effect as to properties, but the working temperatures for such alloys are preferably slightly increased, depending on the proportion of tungsten in the alloy.

In accordance with our invention, we propose to Work the metal first at a temperature above that of recrystallization, such as at about 1400 C. to 1450 C., and then work at a temperature below recrystallization, such as one at about 950 C. to 1000 C. The working above recrystallization temperature is desirably confined to a single swaging, rolling, or other deforming pass, while the swaging or other working below recrystallization temperature is desirably carried on during two or more passes, with soaking or annealing in a hydrogen atmosphere at temperatures between about 950 and 1000 C. between passes. By such treatment, we propose to secure exceptionally uniform grain structure, high hardness, augmented ultimate strength, and a higher as Worked elongation than has been obtained previously when working such materials. We have also found that ice such material processed in this way has minimum porosity.

As an example of what has been done, We desirably start with a hydrostatically pressed cylindrical slug or bar, conveniently about 1.375 in diameter. Such a bar after pressing is sintered in a furnace in accordance with conventional practice to about .950" diameter. We then propose to swage such a bar down to a diameter of about .500" in accordance with the following schedule.

First pass, down to about .710 diameter, while at a temperature of about 1450 C.

Second pass, swage from .710" diameter to .600" diameter, while at a temperature of about 1000 C.

Third pass, swage from .600" diameter to .500" diameter, while at a temperature of about 1000" C.

After the first pass, .the bar was air-quenched to avoid recrystallization, and then soaked in hydrogen for about 15 minutes at a temperature of about 1000 C. before taking the second pass, The material was returned to the furnace after the second pass and soaked in hydrogen for about 15 minutes at about -1000 C. before taking the third or final pass. After the third pass the bar was air-quenched to room temperature.

From the foregoing, it will be seen that the bar treated in accordance with our invention is desirably reduced in area about 44% during a first pass at a temperature above recrystallization, about 28% during a second pass at a temperature below recrystallization, and about 30% during a third and final pass of a temperature below recrystallization. It will also be seen that the total area reduction from initial size to final size is about 72%, and critical temperatures are specified.

Upon testing material as above treated and which con-. tained .1% of cobalt, we found the following as worked properties, meaning the properties without further heattreatment or annealing:

Hardness V.P.N 236 Yield point p.s.i 107,000

Ultimate strength ..p.s.i 117,000

Elongation percent 39 Grain count A.S.T.M 9-10 desirably slightly higher, or approximately 1450 to 1475 C., as compared with '1400" to 1450" C. for the molybdenum-cobalt alloys.

Likewise, the forging or other working temperature below recrystallization for pure molybdenum, and such including the minima in alloying ingredients above specified, is desirably increased to about 1000 C. to 1050 C. as compared with 950 C. to 1000 C. for the molybdenum-cobalt alloys. The working temperatures for molybdenum-tungsten alloys, within the specified range of up to 25% tungsten (or from 1% to 25%), are desirably about the same as for pure molybdenum. Likewise, the annealing or soaking temperature after forging is desirably increased to about 1000 C. to 1050 C. for pure molybdenum and such including the minima in alloying ingredients above specified, as well as for molybdenum alloyed with tungsten within the specified range.

Although preferred embodiments have been disclosed, it will be understood that modifications may be made within the spirit and scope of the invention.

We claim:

1. The method of manufacturing ductile metal from a pressed and sintered article of powdered particles of the group consisting of molybdenum and alloys thereof with small proportions of metal selected from the group consisting of cobalt, nickel, iron and tungsten, comprising working said article to reduce its cross-sectional area while at a temperature of between about 1400 C. and 1475" C., air-quenching said worked article to a temperature below its recrystallization temperature, soaking said quenched article in a protective atmosphere for about 15 minutes at a temperature of about 950 C. to 1050 C., working said soaked article to reduce its cross-sectional area while at a temperature of about 950 C. to 1050 C., soaking said worked article in a protective atmosphere for about 15 minutes at a temperature .of about 950 C. to 1050 C., working said soaked article to further reduce its cross-sectional area while at a temperature of about 950 C. to 1050 C., and finally air-quenching said worked article to room temperature.

2. The method of manufacturing ductile metal from powdered particles of the group consisting of molybdenum and alloys thereof with small proportions of metal selected from the group consisting of cobalt, nickel, iron and tungsten which have been pressed and sintered to form a generally cylindrical article about .95" in diameter, comprising swaging said article to reduce its diameter to about .71" while at a temperature of between about 1400 C. and 1475 C., air-quenching said swaged article to a temperature below its recrystallization temerature, soaking said quenched article in a hydrogen atmosphere for about 15 minutes at a temperature of about 950 C. to 1050 C., swaging said soaked article to reduce its diameter to about .60" while at a temperature of about 950 C. to 1050 C., soaking said swaged article in a hydrogen atmosphere for about 15 minutes at a temperature of about 950 C. to 1050 C., swaging said soaked article to further reduce its diameter to about .50" while at a temperature of about 950 C. to 1050 C., and finally air-quenching said swaged article to room temperature.

3. The method of manufacturing ductile metal from a pressed and sintered article of powdered particles of molybdenum alloyed with from .05% to .3% of cobalt, comprising swaging said article to reduce its cross sectional area while at a temperature of about 1400 C. to 1450 C., air-quenching said swaged article to a temperature below its recrystallization temperature, soaking said quenched article in a hydrogen atmosphere for about 15 minutes at a temperature of about 950 C. to 1000 C., swaging said soaked article to reduce its crosssectional area while at a temperature of about 950 C. to 1000 C., soaking said article in a hydrogen atmosphere for about 15 minutes at a temperature of about 4 950 C. to 1000 C., swaging said soaked article to further reduce its cross-sectional area while at a temperature of about 950 C. to 1000 C., and finally air-quenching said swaged article to room temperature.

4. The method of manufacturing ductile metal from a pressed and sintered article of powdered particles of the group consisting of molybdenum alloyed with from .1% to 5% of metal of the group consisting of nickel and iron, comprising swaging said article to reduce its cross-sectional area while at a temperature of about 1400 C. to 1450 C., air-quenching said swaged article to a temperature below its recrystallization temperature, soaking said quenched article in a hydrogen atmosphere for about 15 minutes at a temperature of about 950 C. to 1000 C., swaging said soaked article to reduce its cross-sectional area while at a temperature of about 950 C. to 1000 C., soaking said article in a hydrogen atmosphere for about 15 minutes at a temperature about 950 C. to 1000 C., swaging said soaked article to further reduce its cross-sectional area while at a temperature of about 950 C. to 1000 C., and finally air-quenching said swaged article to room temperature.

5. The method of manufacturing ductile metal from a pressed and sintered article of powdered particles of the group consisting of molybdenum and alloys thereof with tungsten up to 25%, comprising swaging said article to reduce its cross-sectional area while at a temperature of approximately 1450 C. to 1475 C., air-quenching said swaged article to a temperature below its recrystallization temperature, soaking said quenched article in a hydrogen atmosphere for about 15 minutes at a temperature about 1000 C. to 1050 C., swaging said soaked article to reduce its cross-sectional area while at a temperature of about 1000 C. to 1050 C., soaking said said article in a hydrogen atmosphere for about 15 minutes at a temperature about 1000 C. to 1050" C., swaging said soaked article to further reduce its cross-seetional area while at a temperature of about 1000 C. to 1050 C., and finally air-quenching said swaged article to room temperature.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Preprint 89-30 of the Electro Chemical Society, pp. 377-384, publ. 1946.

Treatise on Powder Metallurgy, by Goetzel, vol. 1, pp. 666-669, publ. 1949. 

1. THE METHOD OF MANUFACTURING DUCTILE METAL FROM A PRESS AND SINTERED ARTICLES OF POWERED PARTICLES OF THE GROUP CONSISTING OF MOLYBDENUM AND ALLOYS THEREOF WITH SMALL PROPORTIONS OF METAL SELECTED FROM THE GROUP CONSISTING OF COBALT, NICKEL, IRON AND TUNGSTEN, COMPRISING WORKING SAID ARTICLES TO REDUCE ITS CROSS-SECTIONAL AREA WHILE AT A TEMPERATURE OF BETWEEN ABOUT 1400* C. AND 1475* C., AIR-QUENCHING SAID WORKED ARTICLE TO A TEMPERATURE BELOW ITS RECRYSTALLIZATION TEMPERATURE, SOAKING SAID QUENCHED ARTICLE IN A PROTECTIVE ATMOSPHERE FOR ABOUT 15 MINUTES AT A TEMPERATURE OF ABOUT 950* C. TO 1050* C., WORKING SAID SOAKING ARTICLE TO REDUCE ITS CROSS-SECTIONAL AREA WHILE AT A TEMPERATURE OF ABOUT 950* C. TO 1050* C., SOAKING SAID WORKED ARTICLE IN A PROTECTIVE ATMOSPHERE FOR ABOUT 15 MINUTES AT A TEMPERATURE OF ABOUT 950* C. TO 1050* C., WORKING SAID SOAKED ARTICLE TO FURTHER REDUCE ITS CROSS-SECTIONAL AREA WHILE AT A TEMPERATURE OF ABOUT 950* C. TO 1050* C., AND FINALLY AIR-QUENCHING SAID WORKED ARTICLE TO ROOM TEMPERATURE. 